Within the modern network space, the Synchronous Optical Network (SONET)/Synchronous Digital Hierarchy (SDH) protocol is becoming increasingly popular as a mechanism for data transport. In this respect, SDH is the European equivalent of the SONET transmission standard. Accordingly, all references in this application to SONET should be understood to also refer to SDH.
Under the SONET/SDH architecture, connections through the network core, and between end-user communications devices, are constructed using a layered model. Each layer (or level) uses connections established at lower levels to build connections spanning progressively larger portions of the network. Within the network core, Section and Line-level connections are established. Section-level connections (commonly referred to as sections) are set-up between topologically adjacent nodes (which may, for example, be cross-connects, regenerators or Add-Drop-Multiplexors) of the network, and correspond to individual hops of an end-to-end connection. Line-level connections (commonly referred to as lines) are set-up between nodes (such as cross-connects or Add-Drop-Multiplexors) capable of processing line overhead within data signals. Regenerators are usually capable of terminating only sections, whereas cross-connects and Add-Drop-Multiplexors will normally terminate both sections and lines. Lines typically span one or more sections.
An end-to-end connection between nodes at which a data signal is multiplexed and demultiplexed uses a path-level connection (usually referred to as a Path). A path commonly spans multiple lines, and may extend beyond the network core to terminate at suitable end-user communications equipment (such as concentrator access switches or service provider routers).
The SONET/SDH protocol provides conventional methods for validating sections, lines and paths. These include section trace, section parity, and line parity checks which implement integrity and validation within one section or one SONET/SDH line. Telecordia TR-253 describes a Path Trace implementation, which enables an end-to-end validation of a path. Path parity implements a path level integrity check. Tandem connection monitoring implements additional integrity checks within the path level. These path-level integrity checks utilize validation, parity and fault indication data that are inserted into Synchronous Payload Envelopes (SPEs) of signals being transported through the path, typically embedded within the path overhead (POH).
Co-assigned U.S. Pat. No. 6,735,170 which issued on May 11, 2004, and entitled METHOD AND SYSTEM FOR ESTABLISHING CONTENT-FLEXIBLE CONNECTIONS teaches a technique for establishing an open connection (OP-N), mapped across a communications network. The OP-N connection is “concatenatable”, in that an end user can transport arbitrarily concatenated signal traffic through the OP-N connection. In principle, virtually any combination of concatenated and non-concatenated signals may be used, up to the bandwidth capacity of the OP-N connection. The traffic mixture (i.e., the mix of concatenated and non-concatenated traffic) within the OP-N connection can be selected by the end user to satisfy their requirements, and may be changed by the end user as those requirements change, without requiring re-configuration of the OP-N connection.
The OP-N connection described in the above-referenced co-pending patent application is constructed using a layered model, in a manner analogous to conventional SONET/SDH connections. The layers of an OP-N connection are designed to fit between the SONET/SDH Line and Path layers. In general, an OP-N connection is expected to span multiple lines, and yet be shorter than an end-to-end Path. An OP-N connection may carry multiple paths and will be set up and validated prior to the establishment of any paths through it. Accordingly, it is necessary to implement a technique for validating OP-N connections independently of any Path-level connections.
Thus there is a need for a method and apparatus for validating an OP-N connection mapped through a communications network between arbitrary end-points.